The skin of a hazelnut is bitter, and that’s why recipes like the Hazelnut Waffles call for skinning the nuts. Here are two ways to skin them yourself. (For both methods: Let the nuts cool completely before using or before storing in a sealed container in the freezer for up to three months.)
The toasting method
Spread the nuts in a single layer on a baking sheet and toast in a 375°F oven until the skins are mostly split and the nuts are light golden brown (the skins will look darker) and fragrant, about 10 minutes. Don’t overtoast or the nuts will become bitter. Wrap the hot nuts in a clean dishtowel and let them sit for 5 to 10 minutes. Then vigorously rub the nuts against themselves in the towel to remove most of the skins. Try to get at least half of the skins off. This may take a lot of rubbing, so be persistent.
Pros: The nuts get toasted and skinned all in one step; uses the oven (which might be heating anyway for whatever you’ll be making with the nuts) rather than dirtying a saucepan.
Cons: Almost impossible to get the nuts completely skinned; stains a dishtowel (so don’t use one you really care about).